The world's fifth-largest oil company, Chevron, has invested $300m (£173m) a year in technology to support new energy sources, fearing oil and gas prices will continue to rise, one of the company's leading figures has told the BBC.

Peter Robertson, the oil giant's Scottish-born vice chairman, said that the company is putting the money into biodiesel and ethanol research, as it is "very important" for the long-term future of the company.

"In 30 years' time, oil and gas will be Chevron's core business - 50 years, I'm not sure," he told BBC World Service's The Interview programme.

"Prices will continue to go up, and I think that technology will continue to advance. Somewhere along that road this $300m a year (that Chevron is investing in alternative energy), which will grow, will intersect with the price of gasoline, or petrol, and people will find alternatives."

Energy debate

Mr Robertson said that Chevron - is now selling "energy efficiency" and claimed the company is the biggest producer of geothermal energy in the world.

"It makes good economic sense and we do it - I think it is very important for the future of our business," he added.

There is a huge debate going on in our country

Peter Robertson, Chevron vice chairman

Chevron has made efforts to present itself as a leader in the energy debate.

The company has been running a web discussion - called willyoujoinus.com - inviting the views of the public on energy issues such as what fuels they want to use, where their fuel is coming from and how much they want to pay for it.

The home page details how many barrels of crude oil are consumed worldwide during the stay of a visitor to the site.

Mr Robertson said that willyoujoinus.com has had 300,000 hits in the seven months since it started.

"I think there is a huge debate going on in our country, the United States [and] there is probably a huge debate going on in the United Kingdom," he said.

He rebuffed criticism that, as a percentage of the company's $14bn a year profit, the $300m investment in renewable energy products is just two percent; and that effectively, with profits of $38m a day, only nine day's worth of profit is being invested.

"Actually, $300m is a lot of money when you are doing research," he said.

'Informed and realistic'

Mr Robertson admitted that the environmental specifications of many products have greatly changed.

However, he said that the site exists so the debate can be "informed about what is realistic" and what, in the company's view, is actually possible.

Chevron says geothermal energy "makes economic sense"

"We will do our very best to advise, to help people understand what can be done and to see whether we can come up with processes that will provide people with energy from a different source," he added.

And he stressed that the business has no intention of ceasing to reinvest in fossil fuels.

"As long as there is oil and gas that can be produced for customers at reasonable prices, that are better than anything else they've got, we will continue to do what is best for our customers - that's what they want us to do," he said.

"People want this product, they want to buy the product. We are in business to produce the products that people want.

"As soon as our customers tell us they don't want it, or vote it down, or do something like that, we will do something else."